Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Goes well beyond the annotations: it discloses cost ("Free") and, critically, the duplicate-call semantics — the same call within 2 minutes returns the existing event with deduplicated: true instead of creating a second one. That time-boxed behavior cannot be expressed by idempotentHint: false, so the description is adding genuine value rather than restating the annotation, and it does not contradict it (outside the 2-minute window duplicates are still possible).

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Three short sentences, front-loaded with purpose before the scoping caveat and the dedup behavior. The one-word sentence "Free." is terse but does carry real information; slightly tighter phrasing could fold it into the prior sentence.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists and all parameters are documented, so the description only had to cover cost and duplicate-call behavior, which it does. What remains unsaid is what the returned object contains beyond deduplicated: true and whether repeated calls outside the window are safe — minor given the output schema.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 83% and every parameter including brandId, markets and description already carries its own description, so the baseline is 3. The prose adds only a weak hint that the event "belongs to the brand," implying brandId scoping, but no format, default, or constraint detail beyond the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ("Add an event to the brand's marketing calendar") and scopes it with concrete examples (launch, promotion, campaign moment). It also delimits the resource against adjacent content ("separate from the holidays and cultural moments Rawa curates") and, by virtue of "Add", is distinguishable from list_calendar_events, update_calendar_event and delete_calendar_event.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Usage is implied by the examples of what counts as a calendar entry and by the note that it is "Free," so an agent can infer this is the cheap way to record a brand-owned moment. However, no sibling is named and there is no explicit when-not guidance (e.g., use update_calendar_event rather than re-creating, or that this does not cover holidays).

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.